Mobile communication units (MCU), such as cellular phones, personal data assistants (PDA's), and Global Positioning System (GPS) devices are often operated by a user driving or riding in a vehicle, such as an automobile or a truck, for receiving and transmitting information in a variety of formats including telephone conversations, voice mail, and FAX or data transmissions.
If the user wishes to drive the vehicle while communicating through the MCU, it is desirable, and may soon be required by law, that the user be able to operate the MCU in a so-called “hands-free” mode, wherein the user does not need not hold the MCU or press any buttons or keys to communicate through or control the MCU.
To allow hands-free operation, an MCU is sometimes permanently mounted in a vehicle, or adapted to fit into a cradle permanently mounted inside the cabin of the vehicle. Such a permanently mounted or cradle mounted MCU is commonly known as an on-board Vehicle Communication Unit (VCU). A vehicle communication unit may include a variety of input/output devices in the passenger cabin of the vehicle to aid the user in communicating through the VCU. These input/output devices may include keyboards, buttons or touch=screens, data ports, or a video screen for displaying incoming information and controlling the VCU. The VCU may also include a loudspeaker and a microphone in the cabin so that the user can hear incoming audio messages without using an ear-piece or headset, and a microphone so that the user can communicate through the VCU by simply speaking within the vehicle cabin.
For optimal hands-free communication, the VCU must allow the user to operate and control the VCU while driving the vehicle, without requiring the driver to divert his gaze and hands from the task of driving to receive input information, or to locate and actuate buttons, keyboards, or other input/output devices. In this regard, it is desirable that the VCU allow the user to receive incoming information from the VCU as audio enunciated in the cabin, and communicate through VCU by simply speaking within the cabin in a normal tone or voice.
It is also desirable that the user be able to control the VCU, and perform such tasks as switching between VCU functions or dialing phone numbers with spoken voice-commands that are recognizable by voice-recognition (VR) devices or software within the VCU. It is highly desirable that the user be able to utilize voice-control by simply speaking a voice-command while simultaneously hearing the enunciated audio. A user would thus be able to hear incoming voice mail messages, for example, or hear navigation information, while simultaneously using voice-commands to step through a list of voice mail messages, or to dial a telephone number with voice-commands.
For the user to be able to dial numbers, or communicate numeric commands over a standard telephone communication system, it is necessary that the VR system be able to generate signals in a format known as Dual Tone Multiple Frequency (DTMF). Unfortunately, however, prior vehicle communication units do not allow the user to utilize voice-control to generate DTMF signals by simply speaking a voice-command while simultaneously hearing the enunciated audio. Existing voice-recognition devices and software require a much higher degree of purity in the voice-command for effective VR control that is required for normal telephone conversations. Where the VCU enunciates audio into the cabin of the vehicle, the enunciated audio is acoustically linked and combined with any spoken voice-command from the user. The microphone of the VCU simultaneously receives both the enunciated audio and the spoken voice-command, together with any background noise in the cabin. The enunciated audio signal and background noise contaminates, or garbles, the voice-command to such an extent that the VR device or software has difficulty discerning that the contaminated audio received by the microphone contains a VR command. Even if the VR system does successfully detect that the combined audio signal received by the microphone contains a voice-command, the VR system may still be unable to discern exactly what command has been given. The VR system cannot generate the DTMF signal desired by the user until it both detects and can discern what voice-command the user has spoken.
What is needed, therefore, is an improved VCU providing a solution to one or more of the problems defined above.